This invention relates to a facsimile apparatus which is capable of efficiently transferring an enlarged or reduced picture image.
In facsimile operations, a situation occasionally arises in which the picture image to be transmitted is either larger or smaller than the paper upon which it is to be recorded. Ordinarily, this problem is overcome by enlarging or reducing the picture image at the transmission facsimile unit.
FIGS. 1A and 1B illustrate a process for enlarging a picture image to 125% of its original size. The facsimile unit at the transmitting side enlarges the original picture information bits 1 (represented by the mark O) by inserting one bit for every three bits in both scanning directions. That is, an expansion bit 2 (represented by the mark X) is inserted at every interval of three information bits in the main scanning direction and one line of expansion bits are inserted at intervals of three information bit lines in the subscanning direction. The method of determining the signal status of the expansion bits is well known in the art, and therefore the explanation thereof is omitted.
FIGS. 2A and 2B show a process for reducing the picture image to 75% of its original size. The facsimile unit at the transmitting side determines original picture information bits 4 to be omitted (represented by the mark .DELTA.) among the original information bits 3 and 4 (represented by the mark O or .DELTA.) as shown in FIG. 2A, such that one bit of every four information bits in the main scanning direction and one of every four lines of information bits in the subscanning direction is eliminated when transmission is subsequently effected (as shown in FIG. 2B).
If picture image processing is achieved in the foregoing manner at the transmission side of the facsimile apparatus, it is not necessary to consider the relation between the transmitting and receiving sides of the facsimile system. In other words, the foregoing expansioncompression method does not depend upon any operation being carried out at the receiving end. Accordingly, this method is advantageous in that it results in increasing the capability of communications with other kinds of communication systems. However, if picture image processing is undertaken only at the signal transmitting side, in the case of picture image enlargement as shown in FIGS. 1A and 1B, the time necessary for signal transmission increases by 25% (since there is 25% more data to be transmitted).